Discovery technique for physical media interface aggregation

ABSTRACT

Various discovery techniques are described for physical media interface aggregation.

BACKGROUND INFORMATION

Communication systems may communicate over a link, such as copper lines,coaxial cable, fiber optic lines and the like. In some cases, aplurality of links may be combined to form a logical link having agreater data rate. However, current techniques to perform linkaggregation are inadequate. A need may exist for an improved techniqueto accomplish link aggregation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a node according to an exampleembodiment.

FIG. 2 is a block diagram illustrating a system according to an exampleembodiment.

FIG. 3 is a diagram illustrating operation of a system according to anexample embodiment.

DETAILED DESCRIPTION

In the detailed description, numerous specific details are set forth inorder to provide a thorough understanding of the embodiments of theinvention. It will be understood by those skilled in the art, however,that embodiments of the invention may be practiced without thesespecific details. In other instances, well-known methods, procedures andtechniques have not been described in detail so as not to obscure theforegoing embodiments.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations may be the techniques usedby those skilled in the data processing arts to convey the substance oftheir work to others skilled in the art.

An algorithm is here, and generally, considered to be a self-consistentsequence of acts or operations leading to a desired result. Theseinclude physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers or the like.It should be understood, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as processing, computing, calculating,determining, or the like, refer to the action or processes of a computeror computing system, or similar electronic computing device, thatmanipulate or transform data represented as physical, such aselectronic, quantities within the registers or memories of the computingsystem into other data similarly represented as physical quantitieswithin the memories, registers or other such information storage,transmission or display devices of the computing system.

Embodiments of the present invention may include apparatuses forperforming the operations herein. This apparatus may be speciallyconstructed for the desired purposes, or it may comprise a generalpurpose computing device selectively activated or reconfigured by aprogram stored in the device. Such a program may be stored on a storagemedium, such as, but is not limited to, any type of disk includingfloppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-onlymemories (ROMs), random access memories (RAMs), electricallyprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read only memories (EEPROMs), flash memory, magnetic oroptical cards, or any other type of media suitable for storingelectronic instructions, and capable of being coupled to a system busfor a computing device.

The processes and displays presented herein are not inherently relatedto any particular computing device or other apparatus. Various generalpurpose systems may be used with programs in accordance with theteachings herein, or it may prove convenient to construct a morespecialized apparatus to perform the desired method. The desiredstructure for a variety of these systems will appear from thedescription below. In addition, embodiments of the present invention arenot described with reference to any particular programming language. Itwill be appreciated that a variety of programming languages may be usedto implement the teachings of the invention as described herein.

In the following description and claims, the terms coupled andconnected, along with their derivatives, may be used. In particularembodiments, connected may be used to indicate that two or more elementsare in direct physical or electrical contact with each other. Coupledmay mean that two or more elements are in direct physical or electricalcontact. However, coupled may also mean that two or more elements maynot be in direct contact with each other, but yet may still cooperate orinteract with each other.

It is worthy to note that any reference in the specification to “oneembodiment” or “an embodiment” means in this context that a particularfeature, structure, or characteristic described in connection with theembodiment may be included in at least one embodiment of the invention.The appearances of the phrase “in one embodiment” or “an embodiment” invarious places in the specification do not necessarily refer to the sameembodiment, but may be referring to different embodiments.

It should be understood that embodiments of the present invention may beused in a variety of applications. Although the present invention is notlimited in this respect, the circuits and techniques disclosed hereinmay be used in many apparatuses, including a variety of nodes. A node,for example, may be any computing system, although the invention is notlimited thereto. By way of example, a node may include a computer, aserver, a bridge, a router, a switch, a wireless node such as a personaldigital assistant (PDA), a cellular phone, a wireless node as part of anInstitute of Electrical and Electronics Engineers (IEEE) 802.11 wirelessLAN (WLAN) such as an 802.11 WLAN mobile or an 802.11 access point (AP).

A node may also comprise a modem, network interface controller and otherdevices to interface with a network, such as a telephone line (e.g.,copper twisted pair lines), a digital subscriber line (DSL), an IEEE802.3 Ethernet network, a local area network (LAN), an AsynchronousTransfer Mode (ATM) network, Internet Protocol (IP) network, a cablenetwork, and the like. The nodes may communicate over a variety ofmedia, such as copper twisted pair lines or conductors, coaxial cable,fiber optic lines, wireless channels, etc. In an example embodiment, thecircuits and techniques described herein may be provided within a cablemodem, a DSL modem, an Ethernet network interface controller (NIC), andthe like.

As used herein, the term packet may include a unit of data that may berouted or transmitted between nodes or stations or across a network. Asused herein, the term packet may include frames, protocol data units orother units of data. A packet may include a group of bits, which mayinclude one or more address fields, control fields and data, forexample.

Referring to the Figures in which like numerals indicate like elements,FIG. 1 is a diagram illustrating a node according to an exampleembodiment. In this illustrative embodiment, a node 100 may include, forexample, a processor 105 to execute instructions and software. Theprocessor may be coupled to a memory and input/output (I/O) controller115 via a host bus 110. Memory and I/O controller may control mainmemory 120 and may control a variety of different I/O interfaces. Anetwork interface 125 is coupled to the memory and I/O controller 115 tointerface node 100 to a network 130.

FIG. 2 is a block diagram illustrating a system according to an exampleembodiment. A customer premises equipment (CPE) node 200 (customer node)may be provided, and may also be referred to as a subscriber node. CPEnode 200 may include a processor, memory and the like.

CPE 200 may also include a media access control (MAC) 205 to handletasks related to media access. CPE 200 may include at least one physicalmedia interface (PHY) 220 coupled to MAC 205, such as PHYs 220A, 220Band 220B. PHYs 220 may, for example, generate signals having the timingand electrical qualities that may be appropriate for transmission over aparticular physical media or link. According to an example embodiment,PHY 220 may include a physical media dependent (PMD), although theinvention is not limited thereto. PHY 220A may be coupled to a link 222,while PHY 220B may be coupled to a link 224. While three PHYs areillustrated in CPE node 200, CPE node 200 may include any number ofPHYs.

CPE 200 may also include a PHY aggregation 210 to assist in aggregatingat least two PHYs into a single logical link. As shown in FIG. 2, PHYs220A and 220B, for example, may be aggregated to form a single logicallink 226, although the invention is not limited thereto. For example,five 2 Mb/s PHYs may be advantageously combined to form a single logicallink have a data rate of 10 Mb/s. According to an example embodiment, upto 32 PHYs may be aggregated to form a single logical link.

CPE node 200 may also include at least one remote discovery register(RDR) 215. RDR 215 may be a readable and writeable register that may beused to facilitate PHY aggregation. In an example embodiment, there maybe an RDR 215 for each MAC (such as MAC 205), although the invention isnot limited thereto. There may be at least one PHY 220 corresponding toa RDR 215. For instance, PHYs 220A, 220B and 220Z may correspond to RDR215.

In another embodiment, a CPE node may include a plurality of MACs, eachwith a corresponding RDR. A different group of PHYs at a CPE node maycorrespond to each RDR, although the invention is not limited thereto.

A central office (CO) node 240 may be a node located near a centraloffice, although the invention is not limited thereto. The centraloffice may be, for example, a telephone network central office, aDigital Subscriber Line (DSL) service central office, a headend at adata over cable network service, and the like. While a CPE node 200 anda CO node 240 are shown in FIG. 2, the invention is not limited thereto.Other types of nodes may be used.

CO node 240 may include a MAC 270, a PHY integration 260 to assist theCO node in controlling PHY aggregation. CO node 240 may include at leastone physical media interface (PHY) 245 coupled to MAC 270, includingPHYs 245A, 245B and 245Z, for example.

Although not shown in FIG. 2, both CPE node 200 and CO node 240 mayinclude a processor, memory and other components typically found in anode or computing system.

In an example embodiment, an RDR 215 that is clear (e.g., having a valueof zero) may indicate that the at least one corresponding PHY is notcurrently allocated for PHY aggregation, and thus, may be available forPHY aggregation. On the other hand, an RDR 215 that is not clear (e.g.,having any value other than zero), may indicate that the correspondingPHY(s) is currently allocated for PHY aggregation. However, other valuesmay be used in RDR 215 to indicate availability to be aggregated, andthe invention is not limited thereto.

In an example embodiment, each CO node 240 may send a message to CPEnode 200 to write a value (an Aggregation Discovery Code) to an RDR 215to allocate the corresponding PHY(s) 220 for aggregation. TheAggregation Discovery Code written to RDR 215 may be assigned by the COnode 240, and may be a unique or different value for each CO node,although the invention is not limited thereto. A unique AggregationDiscovery Code (e.g., a unique or different value for each CO node)written to RDR 215 may also assist in locking out (e.g., preventing)other CO nodes from subsequently writing to that RDR, although theinvention is not limited thereto. This lockout mechanism (e.g., based onthe use of an Aggregation Discovery Code written to the RDR 215),therefore, may prevent a second CO node from attempting to allocate aPHY for aggregation that has already been allocated for PHY aggregationby a first CO node.

In an example embodiment, each CO node may, for example, write a MACaddress of its MAC (e.g., Ethernet MAC address of MAC 270) to an RDR 215to allocate the corresponding PHY to PHY aggregation and lock out otherCO nodes from aggregating the corresponding PHY, although the inventionis not limited thereto. Many different values may be written to the RDR215.

According to example embodiments, PHYs 220 and 245 may comprise, forexample, 2BASE-TL and 10PASS-TS PHYs to be used over twisted pair copperwires, although the invention is not limited thereto. These PHYs aremerely illustrative. Other types of PHYs and media may be used.

PHY aggregation, also referred to as link aggregation or loopaggregation, may allow multiple PHYs to be combined together to form asingle higher speed link. According to an example embodiment, PHYaggregation may be accomplished through a discovery procedure between aCO node 240 and a CPE node 200. The discovery procedure may allow the COnode 240 to determine the PHY aggregation capabilities of a CPE node(e.g., whether a PHY has already been allocated for aggregation) byexamining and manipulating (e.g., reading and writing) the contents ofthe CPE node's remote discovery register (RDR) 215.

According to an example embodiment, a PHY aggregation discoveryprocedure may be accomplished through the exchange of handshakingmessages provided by International Telecommunication Union-T (ITU-T)Recommendation G.994.1, “Handshake Procedures for Digital SubscriberLine Transceivers (“G.994.1”), although the invention is not limitedthereto. G.994.1, for example, defines a CL (capabilities list) messagethat may be sent by a CO node to convey a list of capabilities, modes orfeatures. G.994.1 also defines a CLR (capabilities list+request) thatmay be sent by a CPE node to convey a list of capabilities, modes orfeatures, and to request a CL message from the CO node.

According to an example embodiment, additional control fields/controlbits may be added to the G.994.1 CL and CLR messages to facilitate themanipulation of a CPE node's RDR for aggregation discovery. Table 1illustrates additional control fields/bits related to aggregationdiscovery control that may be used according to an example embodiment.These fields are merely an illustrative embodiment, and other fields maybe used.

TABLE 1 Name Description Aggregation Discovery Code e.g., a 48-bit codePHY aggregation discovery  0 = no PHY aggregation action being performed 1 = an action related to PHY aggregation is being performed DiscoveryOperation 01 = Ready (default) 00 = Set if clear 11 = Clear if sameDiscovery Operation Result  0 = discovery operation completedsuccessfully (default)  1 = operation unsuccessful

The Aggregation Discovery Code may be a value, for example, assigned bya CPE node to be written to a RDR 215 (at least under somecircumstances). As noted above, the Aggregation Discovery Code may aunique value in that it may be unique for each CO node (e.g., each COnode may use a different Aggregation Discovery Code), although theinvention is not limited thereto. According to an example embodiment, aCO node 240 may use the Ethernet MAC address of its MAC 270 as itsAggregation Discovery Code, since the Ethernet Address may be a uniquevalue for each MAC, although the invention is not limited thereto. In anexample embodiment, the Aggregation Discovery Code may be 48 bits,although any size may be used.

The PHY Aggregation Discovery field (bit) may be set to a one toindicate that an action is being performed on the CPE node related toPHY aggregation, or a 0 to indicate that the no action related to PHYaggregation is being performed (e.g., current message may be a nullaction).

The Discovery Operation field (bits) may be used by a CO node 240 toquery and manipulate the remote discovery register (RDR) 215 of a CPEnode 200. The default state of the Discovery Operation field may be“Ready” and may, for example, indicate that the CO node is capable ofperforming an operation on the RDR 215.

A CO node 240 may set the Discovery Operation field to “Set if clear” toconditionally set the value of an RDR. A CO node 240 may send a CLmessage including an Aggregation Discovery Code (e.g., its MAC address)and the Discovery Operation field set to “Set if clear.” In response toreceiving this CL message, the PHY aggregation 210 at a CPE node 200 mayperform the following:

1) read or query the contents of the RDR 215;

2) conditional write: write or set the value of the RDR 215 to theAggregation Discovery Code only if the RDR 215 is clear (e.g.,0x000000000000).

According to an example embodiment, RDR 215 should be clear if the PHYis not currently allocated for PHY aggregation. Therefore, using a “setif clear” operation that first checks that the RDR is clear first beforewriting to it may prevent multiple CO nodes from writing to the sameRDR. Therefore, the use of an RDR with a read-conditional writemechanism, for example as described above, may be used to allow only oneCO node at a time to allocate a PHY for aggregation, and may lockoutother CO nodes after the RDR has been set to any non-cleared value.

A CO node may set the Discovery Operation field to “clear if same” inorder to conditionally clear the RDR 215. For example, a CO node 240 mayhave initially set an RDR, and then aggregated the PHY with another PHYto form a logical link for communication. After the communicationsession has ended, the CO node may de-allocate the PHY to allow the PHYto be allocated for aggregation by other CO nodes. To do this, accordingto an example embodiment, the CO node 240 may send a CL message to theCPE node 200, with the Discovery Operation field set to “clear if same”,and providing the CO node's Aggregation Discovery Code. Upon receivingthis CL message, the PHY Aggregation 210 may perform the following:

1) read or query the contents of the RDR 215;

2) compare the contents of the RDR to the Aggregation Discovery Code;and

3) conditional write: Clear the RDR 215 only if the contents of the RDR215 match the Aggregation Discovery Code provided by the CO node.

Therefore, the use of such a “clear if same” command that uses aread-conditional write mechanism, for example as described above, may beused to ensure that only the CO node that currently has allocated a PHY(written to the RDR) may de-allocate the PHY (clear the RDR), althoughthe invention is not limited thereto.

The Discovery Operation Result field is optional, and according to anexample embodiment, may be used by the CPE node (e.g., in a subsequentCLR message) to indicate the success or failure of a discoveryoperation. In an example embodiment, the Discovery Operation Result maybe a zero to indicate that a discovery operation completed successfully(default). The Discovery Operation Result may be set to a 1 to indicatea failure of a discovery operation. For instance, the DiscoveryOperation Result field may be set to 1 if:

1) a link is down; or

2) a “set if clear” operation was requested but the RDR was not clear;or

3) a “clear if same” operation was requested but the RDR did not matchthe Aggregation Discovery Code provided by the CO node.

These are just a few examples, and the invention is not limited thereto.

FIG. 3 is a diagram illustrating operation of a system according to anexample embodiment. Several examples of handshaking between a CO node240 and a CPE node 200 are shown. Example handshaking/message exchangesare shown for several operations, such as for a “Get” operation, for a“Set if clear” operation, and a “Clear if same” operation. Each of theseoperations may be accomplished through, for example, a capabilitiesexchange between a CO node 240 and a CPE node 200. In an exampleembodiment, a capabilities exchange may be performed by exchangingG.994.1 CL and CLR messages. A G.994.1 capabilities exchange mayinclude, for example, a CLR message sent from the CPE node 240 and areply CL message sent from the CO node 200. According to an exampleembodiment, these CL and CLR messages may include a number of fields,such as the fields described in Table 1, to allow a CO node 240 toexamine and manipulate (e.g., read or write) the contents of an RDR 215at a remote CPE node 200. As shown in the example embodiments of FIG. 3,two back-to-back capabilities exchanges may be used, for example, toperform the “Set if clear” and “Clear if same” operations, although theinvention is not limited thereto.

According to an example embodiment, to accomplish a “Get” operation, aCO node 240 may, for example, send a REQ-CLR message 305 to request acapabilities list from the CPE node 200, although the invention is notlimited thereto. The CPE node 200 may reply with a CLR message 310 withthe PHY aggregation discovery bit set to 1 (indicating that the messagerelates to PHY aggregation discovery), and includes the contents of theRDR 215. The CPE node may, alternatively, reply with message 310 duringa handshaking exchange with CO node 240. Upon receiving message 310, theCO node 240 may then read or examine the received contents of the RDR215 from the CPE node 200. In reply to message 310, CO node 240 may senda CL message 315 to complete the capabilities exchange, where the PHYAggregation discovery bit set to zero (e.g., indicating a null actionfor this message). This illustrates an example of how a CO node 240 mayobtain (e.g., Get) the contents of a CPE node's RDR 215, although theinvention is not limited thereto. For example, in another embodiment ofthe Get operation, a CPE node 200 may send a CLR message 310 withoutbeing prompted by a REQ-CLR message from the CO node. This is yetanother example embodiment.

According to an example embodiment, to accomplish a “set if clear”operation, in response to a CLR message 320 from CPE node (e.g., duringhandshaking), CO node 240 may send a CL message 325 in which the PHYAggregation Discovery bit is set to a 1, the Discovery Operation fieldis set to “Set if clear”, and may include an Aggregation Discovery Codefrom the CO node. Upon receipt of message 325, the PHY aggregation 210at the CPE node 200 may write the Aggregation Discovery Code to the RDR215 only if the RDR is clear, according to an example embodiment,although the invention is not limited thereto. The CPE node 200 may thensend a CL message 330, including the new contents of the RDR 215. The COnode 245 may then read or examine the new contents of the RDR to confirmthat that RDR 215 was set to the aggregation discovery code, or not. Inanother embodiment, message 330 may optionally include the result of the“set if clear” operation, provided as the Discovery Operation Result(e.g., a zero if Aggregation Discovery Code was successfully written toRDR 215, otherwise set to one), although the invention is not limitedthereto. The CO node 240 may then reply with a CL message 335 tocomplete the capabilities exchange, with PHY Aggregation Discovery bitset to zero (e.g., indicating a null action for this message).

According to an example embodiment, to accomplish a “Clear if same”operation” in response to a CLR message 340 from the CPE node 200, a COnode may send a CL message 345 that includes the Discovery Operationfield set to “Clear if same”, PHY aggregation discovery bit set to 1,and providing the Aggregation Discovery Code. Upon receipt of the CLmessage 345, the PHY aggregation of CPE node 200 may compare thereceived Aggregation Discovery Code to the contents of the RDR 215. PHYaggregation 210 may then clear the RDR 215 only if there is a match,although the invention is not limited thereto. The CPE node 200 may thensend a CLR message 345 including the new contents of the RDR. CO node245 may read the new contents of the RDR 215 to confirm that the RDR wascleared. In another embodiment, message 345 may optionally include theresult of the “Clear if same” operation as the Discovery OperationResult (e.g., zero if successfully cleared the RDR 215, otherwise set to1 to indicate an unsuccessful operation), although the invention is notlimited thereto. The CO node 240 may then send a CL message 355 tocomplete this capabilities exchange.

In another embodiment, a CO node 240 may set the RDR of a CPE node(thereby allocating to aggregation the at least one PHY corresponding tothe RDR 215). However, there may be multiple MACs at a CPE, and as aresult, it may not be clear that all PHYs at a CPE node have beenallocated for aggregation. In order to confirm which PHYs have beenallocated to aggregation, according to an example embodiment, the COnode may perform a “set if clear” operation on each of the PHYs. In yetanother example embodiment, the CO node 240 may perform a “set if clear”operation on at least one of the PHYs (thereby setting the value of thecorresponding MAC to the CO node's aggregation discovery code), and thenconfirm PHY allocation by performing a “Get” operation on each of thePHYs. However, these are simply additional embodiments, and theinvention is not limited thereto.

While certain features of the embodiments of the invention have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the embodiments of the invention.

1. A method comprising: sending a first message from a first node to asecond node, the second node including a remote discovery register;receiving a second message at the first node, the second messageincluding the contents of the second node's remote discovery register,the contents of the remote discovery register indicating whether a PHYof the second node has been allocated for aggregation.
 2. The method ofclaim 1 wherein the first message comprises a G.994.1 REQ-CLR messageand the second message comprises a G.994.1 CLR message.
 3. The method ofclaim 1 wherein the sending a first message from a first node to asecond node comprises sending a first message from a first node to acustomer node.
 4. A method comprising: receiving a first message at asecond node from a first node, the second node including a remotediscovery register; sending a second message from the second node to thefirst node in response to the first message, the second messageincluding the contents of the second node's remote discovery register,the contents of the remote discovery register indicating whether a PHYof the second node has been allocated for aggregation.
 5. The method ofclaim 4 wherein the first message comprises a G.994.1 REQ-CLR message,and the second message comprises a G.994.1 CLR message, the first nodecomprising a central office node and the second node comprising acustomer node.
 6. A method comprising sending a first message from afirst node to a second node to conditionally set a remote discoveryregister of the second node to an aggregation discovery code provided bythe first node if the remote discovery register is clear, the contentsof the remote discovery register indicating whether a PHY at the secondnode has been allocated for aggregation.
 7. The method of claim 6 andfurther comprising: receiving a second message at the first node, thesecond message including an updated contents of the second node's remotediscovery register.
 8. The method of claim 7 wherein the first messagecomprises a G.994.1 CL message that includes an aggregation discoveryoperation field set to “set if clear” to conditionally set a remotediscovery register of the second node to an aggregation discovery codeif the remote discovery register is clear and the second messagecomprises a G.994.1 CLR message.
 9. The method of claim 7 and furthercomprising the second node determining whether the remote discoveryregister is clear, and then setting the value of the remote discoveryregister to the aggregation discovery code if the remote discoveryregister is clear.
 10. A method comprising: receiving a first message ata second node from a first node, the first message including anaggregation discovery code, the second node including a remote discoveryregister; and the second node, in response to the first message,determining whether the remote discovery register is clear, and thensetting the value of the remote discovery register to the aggregationdiscovery code if the remote discovery register is clear, the contentsof the remote discovery register indicating whether a PHY at the secondnode has been allocated for aggregation.
 11. The method of claim 10wherein the first message includes an aggregation discovery operationfield set to “set if clear,” the method further comprising sending asecond message from the second node to the first node, the secondmessage including an updated contents of the remote discovery register.12. The method of claim 11 wherein the first message comprises a G.994.1CL message and the second message comprises a G.994.1 CLR message.
 13. Amethod comprising sending a first message from a first node to a secondnode to conditionally clear a remote discovery register of the secondnode if the value of the remote discovery register matches anaggregation discovery code provided by the first node, the contents ofthe remote discovery register indicating whether a PHY at the secondnode has been allocated for aggregation.
 14. The method of claim 13wherein the first message includes an aggregation discovery operationfield set to “clear if same,” the method further comprising sending asecond message from the second node to the first node, the secondmessage including an updated contents of the remote discovery register.15. The method of claim 14 wherein the first message comprises a G.994.1CL message and the second message comprises a G.994.1 CLR message.
 16. Amethod comprising: receiving a first message at a second node from afirst node, the first message including an aggregation discovery code,the second node including a remote discovery register; comparing a valueof the remote discovery register to the aggregation discovery code; andclearing the remote discovery register if there is a match between thevalue of the remote discovery register and the aggregation discoverycode, the value of the remote discovery register indicating whether aPHY at the second node has been allocated for aggregation.
 17. Themethod of claim 16 wherein the first message comprises a G.994.1 CLmessage that includes an aggregation discovery operation field set to“clear if same.”.
 18. An apparatus comprising: a Media Access Control(MAC); a PHY coupled to the MAC; a remote discovery register, a value ofthe remote discovery register to indicate whether the PHY has beenallocated for aggregation; and a PHY aggregation, the PHY aggregationadapted to perform a read-conditional write upon the remote discoveryregister to allocate and de-allocate the PHY to PHY aggregation.
 19. Theapparatus of claim 18, wherein the PHY aggregation comprises a PHYaggregation adapted to determine whether the remote discovery registeris clear, and if so, then to set the value of the remote discoveryregister to an aggregation discovery code received from the first node,in response to a “set if clear” request from the first node.
 20. Theapparatus of claim 18, wherein the PHY aggregation comprises a PHYaggregation adapted to determine whether the value of the remotediscovery register matches an aggregation discovery code received fromthe first node, and if so, then to clear the remote discovery register,in response to a “clear if same” request from the first node.
 21. Theapparatus of claim 18, the PHY comprising at least one from the groupcomprising: a 2BASE-TL PHY; and a 10PASS-TS PHY.
 22. The apparatus ofclaim 18 wherein the PHY comprises a plurality of PHYs.
 23. Theapparatus of claim 18 wherein the MAC comprising a plurality of MACs,and the remote discovery register comprising plurality of remotediscovery registers, each remote discovery register corresponding to aMAC.
 24. The apparatus of claim 18 and further comprising a processorcoupled to the MAC, a memory and an input/output controller coupled tothe processor.
 25. The apparatus of claim 19 wherein the aggregationdiscovery code comprises a Media Access control (MAC) address of thenode.
 26. The apparatus of claim 20 wherein the aggregation discoverycode comprises a Media Access control (MAC) address of the node.
 27. Theapparatus of claim 25 wherein the Media access control address comprisesan Ethernet MAC address.
 28. The apparatus of claim 26 wherein the MACaddress comprises an Ethernet MAC address.
 29. A method comprising:performing PHY aggregation discovery, including, in response to amessage received at a second node from a first node, performing aread-conditional write operation upon a remote discovery register at thesecond node to perform at least one of allocate and de-allocate a PHY atthe second node to PHY aggregation.
 30. The method of claim 29, themethod further comprising, in response to a “set if clear” request fromthe first node, determining at the second node whether the remotediscovery register is clear, and if so, then to set the value of theremote discovery register to an aggregation discovery code received fromthe first node.
 31. The method of claim 29, and further comprising, inresponse to a “clear if same” request from the first node, determiningat the second node whether the value of the remote discovery registermatches an aggregation discovery code received provided by the firstnode, and if so, then clearing the remote discovery register.
 32. Amethod of PHY aggregation discovery comprising: exchanging CL(capabilities list) and CLR (capabilities list+request) messages betweentwo nodes to manipulate a remote discovery register at one of the nodes;said exchanging comprising at least one from the group comprising:sending a “set if clear” request message including an aggregationdiscovery code to conditionally set a value of the remote discoveryregister to the aggregation discovery code; and sending a “clear ifsame” request message including an aggregation discovery code toconditionally clear a node's remote discovery register.
 33. The methodof claim 32 wherein the sending the “set if clear” request messagecomprises: sending a first message from a first node to a second node,the first message having a discovery operation field set to “set ifclear”, the set if clear message including an aggregation discoverycode, the second node including a remote discovery register; determiningif the remote discovery register is clear; setting a value of the remotediscovery register to the aggregation discovery code if the remotediscovery register is clear.
 34. The method of claim 33 wherein thesending a first message from the first node to the second node comprisessending a G.994.1 CL message from a first node to a second node.
 35. Themethod of claim 33 wherein the sending a first message from the firstnode to the second node comprises sending a G.994.1 CL message from acentral office node to a customer node.
 36. The method of claim 32wherein the sending the “clear if same” message comprises: sending afirst message from a first node to a second node, the first messagehaving a discovery operation field set to “clear if same”, the firstmessage including an aggregation discovery code, the second nodeincluding a remote discovery register; comparing the value of the valueof the remote discovery register to the aggregation discovery code; andclearing the remote discovery register if there is a match between thevalue of the remote discovery register and the aggregation discoverycode.
 37. The method of claim 36 wherein the sending a first messagefrom the first node to the second node comprises sending a G.994.1 CLmessage from a first node to a second node.
 38. A method comprising:receiving a message at a first node from a second node, the second nodeincluding a remote discovery register, said message including thecontents of the second node's remote discovery register, the contents ofthe remote discovery register indicating whether a PHY of the secondnode has been allocated to aggregation.
 39. The method of claim 38wherein the message comprises a G.994.1 CLR message.